Pneumatic control system for a fuel-burning apparatus or the like

ABSTRACT

This disclosure relates to a pneumatic control system for a clothes dryer wherein the flow of fuel to the main burner means is pneumatically controlled in such a manner that the ignition means for the main burner means must be first pneumatically actuated before the pneumatic control system will pneumatically open the fuel supply means to the main burner means, the control system including a pneumatically operated logic &#39;&#39;&#39;&#39;memory&#39;&#39;&#39;&#39; unit to assure that the ignition means is always pneumatically operated before the main burner can be pneumatically operated to its on condition by a pneumatically operated NAND unit each time there is a requirement to turn on the main burner means. The &#39;&#39;&#39;&#39;memory&#39;&#39;&#39;&#39; unit is prevented from transmitting atmosphere therethrough when being switched by its setting signal.

States Patent [54] PNEUMATIC CONTROL SYSTEM FOR A FUEL-BURNING APPARATUSOR THE LIKE [72] Inventor: Douglas R. Scott, Elkhart, ind.

[73] Assignee: Robertshaw Controls Company,

Richmond, Va.

[22] Filed: Jan. 26, 1970 [2]] Appl. No.: 5,709

[52] US. Cl ..43l/67, l37/625.66

[51] Int. Cl ..F23n 5/00 [58] Field of Search ..431/66, 67

[56] References Cited UNITED STATES PATENTS 3,522,662 8/1970 Mueller etal ..43l/67 X 1 inn, 1, i972 Primary ExaminerCarroll B. Dority, Jr.Attorney-Auzville Jackson, Jr., Robert L. Marben and Candor, Candor &Tassone ABSTRACT This disclosure relates to a pneumatic control systemfor a clothes dryer wherein the flow of fuel to the main burner means ispneumatically controlled in such a manner that the ignition means forthe main burner means must be first pneumatically actuated before thepneumatic control system will pneumatically open the fuel supply meansto the main burner means, the control system including a pneumaticallyoperated logic memory" unit to assure that the ignition means is alwayspneumatically operated before the main burner can be pneumaticallyoperated to its on condition by a pneumatically operated NAND unit eachtime there is a requirement to turn on the main burner means. Thememory" unit is prevented from transmitting atmosphere therethrough whenbeing switched by its setting signal.

8 Claims, 2 Drawing Figures PATENTEUJAN181972 SHEET 1 BF 2 INVENTOR.DOUGLAS R. SCOTT and F 7% HIS ATTORNEYS Pmmwmwm 3,635645 sum 2 OF 2INVENTOR. DOUGLAS R. SCOTT HIS ATTORNEYS PNEUMATIC CONTROL SYSTEM FOR AFUEL-BURNING APPARATUS OR TlllllE LTKE This invention is related to thepneumatic control systems and methods set forth in the copending Pat.applications, Ser. No. 717,586, filed Apr. 1, 1968, now U.S. Pat. No.3,522,661, and Ser. No. 732,784, filed May 28, 1968, now US. Pat. No.3,522,662, which are assigned to the same assignee to whom thisapplication is assigned.

It is well known that a fuel-buming apparatus, such as a clothes dryeror the like, has been provided wherein the flow of fuel to the mainburner means thereof is controlled by an electric thermostat means thatwill not permit the flow of fuel to the main burner means until after anelectrical ignition means has been electrically actuated so as to assurethat the flow of fuel to the main burner means will be properly ignited.

The first-aforementioned patent application discloses and claims apneumatic control system for controlling the flow of fuel to a mainburner means of an apparatus or the like in such a manner that theignition means for the main burner means must first be pneumaticallyactuated each time before the control system will permit a flow of fuelto the main burner means.

The second aforementioned patent application relates to a pneumaticcontrol system for a fuel-buming apparatus that has fewer control partsthat the control system of the firstaforementioned patent application aswell as an improved arrangement that is substantially fail safe in thelogic units thereof so that the source of fuel will automatically bedisconnected or not be interconnected to the main burner means upon anyone or combination of a number of possible component failures.

Accordingly, one of the features of this invention is to provide such apneumatic control system which will perform the same functions as thecontrol systems of the aforementioned patent applications whileproviding a more accurate and responsive system.

In particular, the embodiment of this invention provides a pneumaticallyoperated logic memory unit which is utilized in combination with apneumatically operated logic hand unit so that the same must eachreceive particular pneumatic signals from the control system before thenand unit will pneumatically turn on the main burner means, thepneumatically operated logic nand unit only causing the fuel source tobe interconnected to the burner means if the pneumatically operatedignition means of the control system has been first pneumaticallyactuated to ignition condition as will be apparent hereinafter. Thememory" unit prevents the flow of atmosphere therethrough during theswitching of the memo ry unit by its control signal.

Accordingly, it is an object of this invention to provide an improvedpneumatic control system for a fuel-burning apparatus or the like, thesystem of this invention having one or more of the novel features setforth above or hereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from areading of this description which proceeds with reference to theaccompanying drawings forming a part thereof and wherein:

FIG. 1 is a schematic view illustrating the improved control system ofthis invention.

FIG. 2 is an enlarged, fragmentary view of the pneumatically operatedlogic units of the control system of FIG. 1 with the logic units beingillustrated in cross section.

While the various features of this invention are hereinafter describedand illustrated as being particularly adapted to pneumatically controlthe operation of a domestic clothes dryer or the like, it is to beunderstood that the various features of this invention can be utilizedsingly or in any combination thereof to provide control means for othertypes of apparatus as desired.

Therefore, this invention is not to be limited to only the embodimentsillustrated in the drawings, because the drawings are merely utilized toillustrate one of the wide variety of uses of this invention.

Referring now to FIG. 1, the improved control system of this inventionis generally indicated by the reference numeral 10 and is utilized forcontrolling the operation of a clothes dryer, generally indicated by thereference numeral 11, having a main burner means 12 adapted to beinterconnected to a fuel source manifold 13 by a pair of pneumaticallyoperated valve means 16 and M in a manner hereinafter described.

The apparatus 11 includes an electric motor 15 which rotates theclothes-receiving drum (not shown) of the apparatus 11 during the entirecycle of operation of the apparatus 11 in a conventional manner, theelectric motor 15 being adapted to be interconnected across two powersource leads L and L in a manner hereinafterdescribed.

The electric motor 15 is adapted to drive an eccentric cam 16 that isinterconnected to its output shaft 17 as long as the electric motor 15is energized whereby the eccentric cam 16 will continuously move apiston rod arrangement 18 to operate a vacuum pump means 19 so as toprovide a continuous vacuum source for the system 10 of this inventionas long as the electric motor 15 is energized, the vacuum pump means 19having its inlet 20 interconnected to a conduit means 21.

The power source lead L is interconnected to one side 22 of the electricmotor 15 by a lead 23. The other power source lead L is interconnectedby a lead 241 to a conventional timeroperated switch blade 25 that hasits contact 26 cooperable with a fixed contact 27 that is interconnectedby a lead 28 to a dryer-door-operated switch blade 29. Thedryer-dooroperated switch blade 29 has a contact 30 cooperable with acontact 31 that is interconnected by a lead 32 to the other side 33 ofthe electric motor 15.

Therefore, it can be seen that in order for the electric motor 15 to beplaced across the power source leads L and L for the electric motor 15to be energized, not only must the dryer door be disposed in its closedposition to close and hold the switch blade 29 against the contact 31,but also the housewife or the like must manually set the cycle timermeans (not shown) of the control system 10 so that the same is in an oncondition to hold the switch blade 25 against the contact 27 for apreset time period after the lapse of which the timer cycle means willautomatically open the switch blade 25 away from the contact 27 toterminate the operation of the control system 10 in a conventionalmanner.

The pneumatically operated valve means 14 and 14' for interconnectingthe fuel source conduit 13 to the main burner means 12 of the apparatus11 are identical in construction and operation and while one such valvemeans could properly control the on-off condition of the main burnermeans 12, the use of two such valve means merely provides a safetyfactor so that if one of the valve means fails, the other valve meanswill still perform its function. Thus, only the pneumatically operatedvalve means 14 will be described and like parts of the valve means Mwill be indicated by like reference numerals followed by a prime mark.

As illustrated in FIG. 1, the pneumatically operated valve means Mcomprises a housing means 35 having a valve seat 36 that interconnectsits fuel source inlet 37 to its fuel source outlet 38, the valve seat 36being opened and closed by a valve member 39 that is moved between itsopened and closed posi tions by a vacuum-operated actuator that isgenerally indicated by the reference numeral 40. The vacuum-operatedactuator 40 comprises a cup-shaped housing member 61 hav ing its openend 42 closed by a flexible diaphragm 43 that is interconnected to thevalve member 39 by a tying means 141 in a conventional manner wherebythe flexible diaphragm 13 cooperates with the housing 41 to define achamber 415 therebetween. A compression spring 416 is disposed in thechamber 15 to tend to normally move the flexible diaphragm 13 upwardlyas illustrated in FIG. 1 to maintain the valve member 39 in its closedposition against the valve seat 36 to prevent any flow of fuel to themain burner means 12. However, when the vacuum source 19 isinterconnected to the chamber 45 in a manner hereinafter described toevacuate the chamber 415, the pressure difierential acting across thediaphragm 43 moves the diaphragm 43 downwardly in opposition to theforce of the compression spring 46 to move the valve member 39 to itsopen position so that the fuel source 13 will be interconnected to themain burner means 12 as long as the pneumatically operated actuators 40and 40 are in their actuated condition.

The ignition means for the main burner means 12 comprises an ignitioncoil 47 having one side 48 thereof interconnected by a lead 49 to thelead 24 through a door-operated switch 29', similar to door switch 29,so that the side 48 of the ignition coil 47 is always interconnected tothe power source lead L when the dryer door is closed. The other side 50of the ignition coil 47 is interconnected by a lead 51 to a switch blade52 that has a contact 53 cooperable with a contact 54 that isinterconnected to the power source lead L by a lead 55.

A vacuum-operated actuator 56 controls the switch blade 52 and comprisesa cup-shaped housing 57 having its open end 58 closed by a flexiblediaphragm 59 that is interconnected to the switch blade 52 by a.suitable tying means 60, the flexible diaphragm 59 cooperating with thehousing 57 to define a chamber 61 therebetween that receives acompression spring 62 that normally tends to urge the flexible diaphragm59 upwardly to hold the switch blade 52 out of contact with the contact54 and thereby maintain the ignition coil 47 in its deenergizedcondition. However, when the chamber 61 of the actuator 56 isinterconnected to the vacuum source 19 in a manner hereinafterdescribed, the resulting pressure differential acting across thediaphragm 59 moves the diaphragm 59 downwardly in opposition to theforce of the compression spring 62 to place the switch blade 52 intocontact with the contact 54 so as to place the ignition coil 47 acrossthe power source leads L and L When the ignition coil 47 is placedacross the power source leads L and L by the vacuum-operated actuator 56in a manner hereinafter described, the ignition coil 47 subsequentlyheats up to a temperature that will be sufficient for igniting fuelissuing from the main burner means 12 in a conventional igniting manner.

An ignition coil temperature-sensing means 63 is provided for the systemand comprises a bimetal member 64 that is interconnected to a valvemember 65 by a typing means 66, the valve member 65 being disposed in ahousing means 67 having a valve seat 68 fluidly interconnecting aconduit 69 to a conduit 70. When the bimetal member 64 senses atemperature of the ignition coil 47 below a temperature sufficient forigniting fuel issuing from the main burner means 12, the bimetal member64 is in such a condition that the same maintains the valve member 65away from the valve seat 68 and against a valve seat 68 that leads tothe atmosphere so as to fluidly interconnect the conduits 69 and 70together. However, when the ignition coil 47 reaches an ignitiontemperature, the bimetal metal member 64 warps in such a manner that thesame moves the valve member 65 against the valve seat 68 to terminatethe fluid connection between the conduits 69 and 70 and opens the valveseat 68 so that atmosphere is interconnected to the conduit 70 for apurpose hereinafter described. in addition, when the main burner means12 is operating, the bimetal member 64 also senses the flames at themain burner means 12 so that the bimetal member 64 will maintain thevalve member 65 in its closed position against the valve seat 68 as longas fuel is burning at the main burner means 12.

Another temperature-sensing device 71 is provided for the control system10 and is adapted to sense the temperature effect of the main burnermeans 12. The temperature-sensing means 71 comprises a bimetal member 72that is interconnected to a valve member 73 by a tying means 74, thevalve member 73 being disposed in a housing means 75 to open and close avalve seat 76 thereof that is adapted to fluidly interconnect theatmosphere with the interior of the housing 75 when the valve seat 76 isopen. However, when the valve seat 76 is closed, the housing 75, ineffect, interconnects the conduit 21 to the conduit 69 of the ignitiontemperature-sensing means 63.

As long as the temperature effect of the burner means 12 of theapparatus 11 is below a predetermined temperature effect setting of thesensing means 71, the bimetal member 72 maintains the valve member 73against the valve seat 76 to, in effect, fluidly interconnect theconduits 21 and 69 together whereby if the electric motor 15 isenergized, the vacuum source 19 will be interconnected to the conduit69. However, when the temperature-sensing means 71 senses a temperatureeffect of the burner means 12 above the set temperature effect settingof the thermostatic means 71, the bimetal member 72 warps in a manner tomove the valve member 73 away from the valve seat 76 and, thus, ineffect, disconnects the vacuum source 19 from the conduit 69 as theatmosphere is now interconnected to the conduit 69 through the openedvalve seat 76 for a purpose hereinafter described. Of course, it is tobe understood that the sensing device 71 could be manually adjustablefor temperature selection purposes by the housewife or the like or couldbe factory set for an optimum drying temperature for the apparatus 11.

The conduit 69 is interconnected by a conduit 77 to a port means 78 of apneumatically operated logic memory unit 79 later to be described, theconduit 77 also being fluidly interconnected to a conduit 80 that leadsto a port means 81 of a pneumatically operated logic nand unit 82 ofthis invention. The conduit 80 has a restriction 83 therein intermediatethe port means 81 of the logic nand unit 82 and the conduit 77.

The conduit 70 leading from the ignition temperaturesensing means 63 isinterconnected to another port means 85 of the logic nand unit 82 aswell as to a conduit 86 that is interconnected to one side 87 of a checkvalve 88, the conduit 70 having a restriction means 89 therein inadvance of the conduit 86.

The check valve 88 comprises a housing means 90 having a valve seat 91adapted to be opened and closed by a valve member 92, the valve seat 91being adapted to interconnect the conduit 86 at the side 87 thereof tothe other side 93 of the check valve 88 that leads to a conduit 94. Thevalve member 92 normally seats against the valve seat 92 to preventfluid communication between the conduits 86 and 94 so that when theconduit 70 is interconnected to the vacuum source 19 by the valve means63 and 71 being disposed in the positions of FIG. 1, the vacuum source19 opens the valve member 92 away from the valve seat 91 so as to beinterconnected to the conduit 94.

The conduit 94 is fluidly interconnected to a conduit 95 that has oneend 96 thereof interconnected to a port means 97 of the logic memoryunit 79 while the other end 98 of the conduit 95 is interconnected toanother port means 99 of the logic memory unit 79.

The conduit 95 is fluidly interconnected to a conduit 101 that leads toa port means 102 of the logic nand unit 82, the logic nand unit havinganother port means 103 thereof fluidly interconnected to a conduit means104 that is fluidly interconnected to branch conduit means 105 and 105'that are respectively fluidly interconnected to the chambers 45 and 45of the vacuum actuators 40 and 40. The branch conduits 105 and 105'respectively have restrictions 107 and 107 therein.

The conduit 104 intermediate the actuators 40 and 40 and the nand unit82 is interconnected to the atmosphere by a controlled bleed means 100for a purpose hereinafter described. However, the controlled bleed means100 interconnects the conduit 104 to the atmosphere at a controlled ratethat is less than the effective rate of fluid interconnection providedby the restriction 83 in the conduit 77 as will be apparent hereinafter.

The conduit 70 leading from the ignition temperaturesensing means 63 isfluidly interconnected to a conduit 106 that is fluidly interconnectedto the chamber 61 of the actuator 56.

A remaining port means 108 of the logic nand unit 82 is interconnectedto the atmosphere through a filter 108' and a port means 109 of thelogic memory unit 79 is interconnected to the atmosphere.

The remaining port means 110 of the memory unit 79 is interconnected bya conduit 110' to the conduit 70 interlOlOl9 0128 mediate therestriction 89 and the sensor n3 for a purpose hereinafter described andto the atmosphere through a restriction 1109, the conduit 1110 having aone-way check valve 99 similar to the check valve 89 whereby like partsare indicated by like reference numerals followed by a prime mark.

As previously stated, the control system 110 is so constructed andarranged that the ignition coil 417 for the burner means 112 must befirst energized to a temperature thereof that will be sufficient forigniting fuel issuing from the burner means l2 each time before theactuators 419 and will be actuated to simultaneously move the valvemembers 39 and 39' from their closed positions to their open positionsto cause fuel to issue from the main burner means 112.

Thus, since both temperature'sensing devices 63 and 711 are normallydisposed in the positions illustrated in FIG. 1 when the control system19 is initially turned on by the housewife or the like setting the timercycle means in its on" position to close the switch blade 25 against thecontact 27, the thusenergized electric motor will operate the vacuumpump 119 and since the temperature effect of the apparatus 111 is belowthe temperature effect setting of the thermostatic device 711, thevacuum pump 119 is adapted to evacuate the conduit 69 through the closedhousing 75 as well as to evacuate the conduit means 79 and 77 leadingrespectively to the logic memory" unit 79 and logic nand unit 32.

The logic nand unit 92 will now receive a pneumatic signal at the portmeans 102 thereof from the memory unit 79 as well as a pneumatic signalat the port means 85 thereof as long as the valve member 65 of theignition temperature-sensing means 63 is in its open position from thevalve seat 68 and is closed against the valve seat 68' whereby the nandunit will be in a deactivated condition to prevent the vacuum source 19from being interconnected to the conduit 1104 so that the valve means141 and M remain in their closed positions to prevent fuel from reachingthe main burner means 112. However, after the ignition coil 47 reachesits ignition condition, the valve means 65 closes against the valve seat68 and opens the valve seat 68' so as to terminate the pneumatic signalto the port means 85 of the nand unit 82 whereby the nand unit 82 willnow be activated to a condition thereof to interconnect the vacuumsource 19 to the conduit 194 so that the actuators 40 and 410 will beevacuated to open the valve members 39 and 39' so that fuel can issuefrom the burner means 12 and be ignited by the ignition means 47Accordingly, the logic units 79 and 82 always require that the valvemember 65 must first be in its open position away from the valve seat asand then be moved to a closed position against the valve seat 68 aftereach closing of the main valve means M and M before the main valve means141 and M can be again opened, the valve member 65 only closing againstthe valve seat as after an open condition thereof by the ignition coil47 being energized to a temperature suitable for igniting fuel that isto subsequently issue from the main burner means 112.

The details of the logic units 79 and 82 for accomplishing the abovefunction will now be described in detail whereby reference is now madeto F116. 2.

As illustrated in FIG. 2, the logic units 79 and 92 are substantiallyidentical in construction whereby only the particular details of thelogic memory" unit 79 will now be described and like parts of the logicnand unit 82 will be indicated by the same reference numerals followedby the reference letter A. In this manner, it will be appreciated thatthe logic units of this invention can be made from the same parts in asimple and effective manner while producing different logic functions aswill be apparent hereinafter so that the cost of the control system it)of this invention is relatively small when considering the costs ofprior-known electrical and pneumatic control systems.

As illustrated in FIG. 2, the logic memory" unit 79 comprises twohousing parts 111 and 1112 suitably secured together to hold two annularmembers 1113 and 1114 between the opposed and respective inner end wallmeans 115 and 1116 thereof. A flexible, one-piece diaphragm member 117is disposed in the housing means 111111 and 11112 and has anintermediate or large central outwardly directed diaphragm portion 1119provided with an outer peripheral portion 11119 that is secured andsealed between the annular members H213 and 1M. An outboard smallerspaced diaphragm portion 120 of the diaphragm member 1117 has its outerperiphery 11211 secured and sealed between the housing member llllll andthe annular member M3 to define a chamber 1122 between the diaphragmportion 120 and the end wall means 115 of the housing member 11111 whilecooperating with the larger central diaphragm portion M8 to define achamber 1123 between the diaphragm portions 11119 and 1129. An opposedsmaller outboard spaced diaphragm portion 1124i of the diaphragm member1117 has its outer periphery secured and seated between the annularmember 11114 and the housing member 11112 to define a chamber 126between the diaphragm portion i241 and the end wall means 11116 of thehousing member 1122 while cooperating with the central diaphragm portionlllfi to define a chamber 127 between the diaphragm portions 1119 and1241.

The diaphragm member 117 has a bore B28 interrupting the end 129 thereofso as to receive a compression spring 1139 that has one end bearingagainst the end wall means 116 of the housing member 11112 and the otherend thereof bearing against the diaphragm member 11117 to normally urgethe diaphragm portion 129 against a frustoconical valve seat 1911 thatprojects inwardly from the end wall means 11115 of the housing memberllllll into the chamber 122. The valve seat means ll3ll of the logicmemory unit 79 is interconnected to the port means 78 thereof that leadsto the conduit 77 whereas the valve seat means 1131A of the nand unit 92is intercon nected to the port means til that leads to the conduit 90.

The diaphragm member 1117 has a passage means 132 passing through thediaphragm portion 129 in offset relation to the valve seat 1131 so as toalways fluidly interconnect the chambers 1122 and 1126 together, thepassage 132 also being in offset relation to a frustoconical valve seat133 that projects inwardly from the end wall means MS of the housingmember 1112 and is received in the bore 128 of the diaphragm member 1117to be opened and closed by the end wall 11341 of the diaphragm member11117 that defines the closed end of the bore 128 and forms part of theeffective surface of the diaphragm portion 124 that defines the chamber1126. The valve seat 1133 of the logic memory unit 79 is interconnectedto the port llll which leads to the conduit 11110 and the valve seat1133A of the logic nand unit 112 is interconnected to the port means 108that leads to the atmosphere.

The port means 78 and 99 of the housing member lllll and the port means110 of the housing member 11112 can comprise outwardly extending tubularnipples that can be effectively telescoped into flexible conduit meansto fluidly interconnect the same to such conduit means, such nippleextensions containing suitable air-filtering means 134'. In theembodiment illustrated in FlG. 2, the nipple port means 99 and 79 of thelogic memory" unit 79 are fluidly interconnected respective ly to theconduits 98 and 70 whereas the nipple port means 811 and 1103 of thelogic nand unit 82 are respectively interconnected to the conduits 8t)and MM.

The annular member 114 carries the port means 97 in the form of a nippleextension projecting out of an opening means 135 in the housing member11112 and the port means 1199 comprises a nipple extension of theannular member llll3 projecting out of an opening means 136 of thehousing member H1. The nipple port means 97 of the logic memory" unit 79is interconnected to the end 96 of the conduit member 95 and the nippleport means 1199 is interconnected to the atmosphere whereas thecorresponding nipple port means 1192 and 95 of the logic nand unit 92are respectively interconnected to the conduits 11911 and 70.

Accordingly, it can be seen that the chamber 1122 of the logic memory"unit 79 always interconnected to the port means 99 and, thus, to the end99 of the conduit 95 whereas the port means 78 and, thus, the conduit 77is adapted to be interconnected to the chamber 122 when the diaphragmmember 117 opens the valve seat 131. The atmosphere port means 109 isalways interconnected to the chamber 123. The chamber 127 is alwaysinterconnected by the port means 97 to the end 96 of the conduit means95. As previously stated, the chamber 126 is always interconnected tothe chamber 122 by the passage means 132 and adapted to beinterconnected to the atmosphere or effectively blocked from theatmosphere at the port means 1 10 except for the controlled rateprovided by the bleed restriction 100 when the diaphragm member 117opens the valve seat 133 depending on whether the valve 88' is open orclosed as will be apparent hereinafter.

In regard to the logic nand unit 82, the chamber 122A thereof is alwaysinterconnected by the port means 103 to the conduit 104 and is adaptedto be interconnected to the port means 81 and, thus, to the conduit 80when the diaphragm member 117A opens the valve seat 131A, the chamber122A always being interconnected to the chamber 126A by the passagemeans 132A in the diaphragm member 117A. The chamber 123A is alwaysinterconnected by the port means 85 to the conduit 70. The chamber 127Ais always interconnected by the port means 102 to the conduit 101. Thechamber 126A, while always being interconnected to the chamber 122A bythe passage means 132A in the diaphragm member 117A, is adapted to beinterconnected to the atmosphere at the port 108 when the diaphragmmember 117A opens the valve seat 133A.

The operation of the control system 10 of this invention will now bedescribed.

Assuming that the dryer door is in its closed position to hold theswitch blades 29 and 29 in their closed positions, the housewife or thelike sets the timer selector means for operating the dryer 11 for apredetermined length of time whereby the timer mechanism closes andholds the switch blade 25 against the contact 27 and will maintain theswitch blade 25 against the contact 27 during the entire cycle ofoperation of the dryer 11 so that at the conclusion of such time period,the timer means will automatically open the blade 25 away from thecontact 27 to terminate the operation of the apparatus 1 1.

With the switch blade 25 now moved to its closed position against thecontact 27, it can be seen that the electric motor is placed across thepower source leads L and L so that the electric motor 15 willcontinuously rotate the laundryreceiving drum to tumble the clothes inan atmosphere to be heated by the burner means 12 for drying of thelaundry or the like. As the output shaft 17 of the motor 15 iscontinuously rotating, the same through the eccentric cam 16reciprocates suitable pumping mechanism of the vacuum pump 19 tocontinuously provide a vacuum source for the control system 10.

At the initial operation of the control system 10, not only is theignition coil 47 not at an ignition temperature, but also thetemperature effect of the apparatus 11 is below the temperature effectsetting of the thermostatic means 71 whereby both valve members 65 and73 are in the position as illustrated in FIG. 1 so that the vacuumsource 19 is not only interconnected to the vacuum-operated actuator 56to evacuate the chamber 61 thereof and close the switch blade 52 againstthe contact 54 to place the ignition coil 47 across the power sourceleads L and L but also the vacuum source 19 is interconnected by theconduits 77 and 80 to the valve seats 131 and 131A of the memory unit 79and nand unit 82, which valve seats 131 and 131A are normally closed bythe diaphragm members 117 and 117A due to the force of the respectivecompression springs 130 and 130A, and by the conduit means 70 to thechambers 127 and 122 of the memory unit 79 and the chamber 123A of thenand unit 82. The vacuum in the conduits 70 and 110' causes the checkvalve 88' to close so that the open valve seat 133 of the memory unit 79is effectively blocked from the atmosphere as the bleed 100 does noteffect evacuation of chamber 126.

In particular, since the conduit 70 is interconnected to the inlet 20 ofthe vacuum pump 19 by the positioned valve members 65 and 73, the vacuumpump 19 can evacuate the chamber 123A of the nand unit 82 to maintainthe diaphragm member 117A thereof in its deactivated and seatingposition against the valve seat 131A so that the vacuum source in theconduit leading to the valve seat 131A cannot reach the actuators 40 and40' to open the valve means 14 and 14.

Also, since the conduit 86 is now being evacuated, the check valve 88opens whereas the check valve 88 closes so that the conduit can beevacuated whereby the end 96 thereof evacuates the chamber 127 of thememory" unit 79 so that the resulting pressure difierential actingacross the large central diaphragm portion 118 causes the diaphragmmember 117 to move upwardly in FIG. 2 in opposition to the force of thecompression spring to its activated position to open the valve seat 131.

However, before, the evacuation of the chamber 127 of the memory" unit79 can effect the switching of the diaphragm member 117 upwardly in FIG.2, the vacuum source 19 now being interconnected to the chamber 126 bythe way of conduit 95, chamber 122 and diaphragm passage 132 to chamber126, assists in the complete evacuation of the chamber 122 so that whenthe diaphragm member 117 does switch to its up position in FIG. 2, noatmospheric pressure is permitted to pass out into the conduit 95 and,thus, slow down or prevent the setting of the memory unit 79 in its on"position.

With the valve seat 131 now being opened by the activated memory unit79, the vacuum source 19 is interconnected by the conduit 77 through therestriction means 83 to the chamber 122 of the memory unit 79 so thatthe conduit 101 effectively leading from the chamber 122 of the memory"unit 79 is evacuated to evacuate the chamber 127A of the nand unit 82.

With the chamber 127A of the nand unit 82 now being evacuated, it can beseen that as long as the valve member 65 of the ignitiontemperature-sensing means 63 is in its seated position against the valveseat 68', the opposing chamber 123A of the nand unit 82 is alsoevacuated so that an equal vacuum condition exists across the centraldiaphragm portion 118A of the diaphragm member 117A of the nand unit 82so that the compression spring 130A maintains the diaphragm member 117Ain its up or deactivated position in FIG. 2 to maintain the valve seat131A thereof closed and the chamber 122A thereof that leads to thechambers 45 and 45 of the actuators 40 and 40 of the valve means 14 and14' interconnected to the atmosphere through the passage means 132A ofthe diaphragm member 117A and the open valve seat 133A whereby the valvemembers 14 and 14 cannot be opened to interconnect the fuel source 13 tothe main burner means 12 as long as a vacuum signal is directed to thechamber 123A by the ignition-sensing means 63.

However, when the energized ignition coil 47 subsequently heats up toignition condition, the sensing member 64 warps downwardly in FIG. 1 toopen the valve seat 68 and close the valve member 65 against the valveseat 68 and thereby disconnect the vacuum source 19 from the conduit 70which begins to return to atmospheric condition by the opened valve seat68' so that not only is the chamber 61 of the actuator 56 returned toatmospheric condition to open the switch blade 52 away from the contact54 and deenergize the ignition coil 47, but also the chamber 123A of thenand unit 82 returns to atmospheric condition whereby the resultingpressure differential acting across the diaphragm portion 118A of thediaphragm member 117A of the nand unit 82 causes the diaphragm member117A to move downwardly in FIG. 2 in opposition to the force of thecompression spring 130A to its activated position to not only open thevalve seat 131A to the chamber 122A, but also to close the valve seat133A from the chamber 126A.

In this manner, since the valve member 73 of thetemperature-effect-sensing means 71 in its open condition, the vacuumsource 19, in effect, is interconnected to the chambers 45 and 45' ofthe actuators 40 and 40 to move the valve members 39 and 39' to theiropen position so that the fuel source 13 is now interconnected to themain burner means 12 and is ignited by the ignition coil 47'.

As previously stated, when the valve member 65 of the ignitiontemperature-sensing means 63 is moved to its closed position against thevalve seat 68 to permit the now-opened valve seat 68 to return theconduit 78 to atmospheric condition to terminate the vacuum signal tothe chamber 123A of the nand unit 82 so as to activate the same, thecheck valve 88 closes so that such return of air into the conduit 78cannot reach the conduit 94 whereby the diaphragm member 117 of thememory" unit 79 remains in its actuated condition wherein the valve seat131 is in its open condition and the valve seat 133 is in its closedcondition so that a continuous vacuum signal is directed from thechamber 122 to the chamber 127A of the NAND unit to maintain the NANDunit in its activated position for maintaining the valve means 14 and 14in their open condition, the restriction 83 providing a greater flowthan the controlled bleed means 108 in the conduit 104 so that the valvemeans 14 and 14 remain open. A holding circuit is provided for thememory unit from the vacuum source 19 to the chamber 122 of the memory"unit 79 and by means of the conduit 95 to the chamber 127 to maintainthe diaphragm member 117 in its up or activated position. Also, thereturn of air into the conduit 78 causes the check valve 88 to openwhereby atmosphere is at the closed valve seat 133 of unit 79.

Thus, since flames now exist at the main burner means 12, thetemperature-sensing means 63 will maintain the valve member 65 closedagainst the valve seat 68 so that the burner means 12 will continue tooperate unless the temperature effect being produced by the burner means12 exceeds the predetermined temperature effect setting of thethermostat means 71.

If the temperature effect of the burner means 12 exceeds the setting ofthe thermostat 71, the temperature-sensing member 72 will move the valvemember 73 away from the valve seat 76 to effectively disconnect theconduit 77 from the vacuum source 19 whereby the air will return notonly to the chamber 127 of the memory unit 79 through the opened valveseat 131 to deactivate the same, but also permit air to return to thechamber 127A of the NAND unit 82 whereby the compression spring 130A ofthe NAND unit 82 will move the diaphragm member 117A upwardly to closethe valve seat 131A and open the valve seat 133A so that the chambers 45and 45' and the actuators 30 and 38 will be interconnected to theatmosphere by the passage means 132A in the diaphragm member 117Aleading to the chamber 126A that is interconnected to the open valveseat 123A that leads to the atmosphere at the port 188 as well as by thebleed means 188 in the conduit 184. Similarly, the diaphragm member 117of the memory" unit 79 moves downwardly in FIG. 2 under the force of thecompression spring 138 because the chamber 127 returns to atmosphericcondition so that the valve seat 131 is now closed and the valve seat133 is opened to return the chamber 126 to atmospheric condition.

Since flames do not now exist at the main burner means 12, the ignitiontemperature-sensing means 63 now causes the valve member 65 to move awayfrom the valve seat 68 and against the valve seat 68' so that when thevalve member 73 of the thermostat 71 is again moved to its closedcondition against the valve seat 76 by the temperature effect in thedryer 11 falling below the set temperature effect of the thermostat '71,the main burner means 12 will be operated in the manner previouslydescribed wherein the igniter means 47 will again be first energized toignition condition before the valve members 14 and 14' can be opened.

However, if during the normal operation of the control system 10,wherein the main burner means 12 has been interconnected to the fuelsource 13 in the manner previously described so as to be continuouslyburning, the housewife or the like should open the dryer doortemporarily to cause the switch blades 29 and 29 to open so as todisconnect the electric motor 15 from the power source leads L and Lwhereby the vacuum source 19 ceases to function so that the controlsystem bleeds to atmospheric condition by the controlled bleed 188, andthe housewife subsequently closes the dryer door to again activate themotor 15 before the ignition temperature-sensing means 63 has moved thevalve member 65 away from the valve seat 68, the NAND unit 82 cannotcause reopening of the valve means 14 and 14' because the "memory unit79 has not been reset to its activated position so as to interconnectthe conduit 77 to the chamber 122 thereof and, thus, to the chamber 127Aof the NAND unit 82 as it requires an opening of the valve member 65away from the valve seat 68 of the ignition temperature-sensing means 63to activate the memory" unit 79 and the NAND unit 82 requires asubsequent closing of the valve member 65 against the valve seat 68 toterminate the vacuum signal to the chamber 123A thereof before the NANDunit 82 can be activated to cause opening of the valve means 14 and 14'.

Thus, it can be seen that the control system 18 of this inventionutilizes only two logic units each formed of identical structure butperforming different logic functions in a manner to control the mainburner means 12 so that the system requires that the ignition means 47be always pneumatically operated to ignition condition before the mainburner means 12 can be pneumatically operated to its on" condition eachtime there is a requirement to turn on the main burner means.

Further, it can be seen that the logic unit 79 of this invention is soconstructed and arranged that during the time of switching the memory"unit 79, no atmospheric signal is seen by the unit 79 to slow down orprevent its switching operation.

Further, any clogging of the restrictions 89 and 83 by dirt or the likeduring the operation of the system 18 will not cause an adversesituation as the bleed means 188 will cause the valve means 14 and 14'to close and thereby terminate the operation of the burner 12.

Thus, it can be seen that this invention provides an improved pneumaticcontrol system for a fuel-burning apparatus or the like.

What is claimed is:

1. A pneumatic control system for a fuel-burning apparatus having burnermeans adapted to be interconnected to a source of fuel comprising asource of pneumatic fluid, pneumatically operated ignition means forsaid burner means, interconnecting means for interconnecting said fuelsource to said burner means, pneumatically operated valve means forcontrolling the flow of fuel from said fuel source to said burner meansthrough said interconnecting means, means for interconnect ing saidpneumatic source to said pneumatically operated i gnition means tooperate the same every time before said pneumatically operated valvemeans is opened, and means for interconnecting said pneumatic source tosaid pneumatically operated valve means to operate the same forinterconnecting said fuel source to said burner means only after saidignition means has been pneumatically operated for igniting said burnermeans, said means for interconnecting said pneumatic source to saidpneumatically operated valve means comprising a pneumatically operatedlogic memory unit, said pneumatically operated logic memory unitproviding an output pneumatic signal from said pneumatic source onlywhen said memory" unit is activated by said means interconnecting saidpneumatic source to said pneumatically operated ignition means, saidmemory" unit being deactivated each time said pneumatically operatedvalve means disconnects said fuel source from said burner means wherebysaid memory" unit terminates its output pneumatic signal untilreactivated by said means interconnecting said pneumatic source to saidpneumatically operated ignition means, said output pneumatic signalbeing required before said means for interconnecting said pneumaticsource to said pneumatically operate valve means can interconnect saidpneumatic source to said pneumatically operated valve means, said memoryunit providing an atmospheric output signal when in a deactivatedcondition thereof, said means interconnecting said pneumatic source tosaid pneumatically operated ignition means interconnecting saidpneumatic source to said memory" unit to not only cause switching ofsaid memory" unit from its deactivated condition to its activatedcondition but also to terminate said atmospheric output signal duringsaid switching operation and thereby prevent an atmospheric outputsignal during the time said memory unit is being switched from itsdeactivated condition to its activated condition.

2. A pneumatic control system as set forth in claim 1 wherein saidpneumatically operated logic memory unit comprises a housing meanscarrying a plurality of spaced diaphragm means that move in unisonrelative to said housing means and cooperate therewith to define aplurality of chambers in stacked relation.

3. A pneumatic control system as set forth in claim 2 wherein saidpneumatic source is directed to one of said chambers to activate saidmemory unit when said pneumatic source is interconnected to saidpneumatically operated ignition means whereby another chamber directssaid output pneumatic signal from said pneumatic source, and meansinterconnecting said other chamber with said one chamber to provide aholding pneumatic circuit means for said memory unit in its activatedcondition.

4. A pneumatic control system as set forth in claim 3 wherein arestriction means interconnects said pneumatic source to said onechamber when said pneumatic source is interconnected to saidpneumatically operated ignition means.

5. A pneumatic control system as set forth in claim 3 wherein said otherchamber and a third chamber of said memory" unit have valve seatsleading thereto to be altemately opened and closed by said diaphragmmeans.

6. A pneumatic control system as set forth in claim 5 wherein said valveseat of said third chamber is adapted to interconnect the atmosphere toits respective chamber when said diaphragm means opens said valve seatof said third chamber and said source is disconnected from saidpneumatically operated ignition means.

7. A pneumatic control system as set forth in claim 6 wherein said valveseat of said other chamber is adapted to interconnect said pneumaticsource to its respective chamber when said diaphragm means opens saidother valve seat.

8. A pneumatic control system as set forth in claim 7 wherein saiddiaphragm means has passage means therein interconnecting said thirdchamber and said other chamber together.

1. A pneumatic control system for a fuel-burning apparatus having burnermeans adapted to be interconnected to a source of fuel comprising asource of pneumatic fluid, pneumatically operated ignition means forsaid burner means, interconnecting means for interconnecting said fuelsource to said burner means, pneumatically operated valve means forcontrolling the flow of fuel from said fuel source to said burner meansthrough said interconnecting means, means for interconnecting saidpneumatic source to said pneumatically operated ignition means tooperate the same every time before said pneumatically operated valvemeans is opened, and means for interconnecting said pneumatic source tosaid pneumatically operated valve means to operate the same forinterconnecting said fuel source to said burner means only after saidignition means has been pneumatically operated for igniting said burnermeans, said means for interconnecting said pneumatic source to saidpneumatically operated valve means comprising a pneumatically operatedlogic ''''memory'''' unit, said pneumatically operated logic''''memory'''' unit providing an output pneumatic signal from saidpneumatic source only when said ''''memory'''' unit is activated by saidmeans interconnecting said pneumatic source to said pneumaticallyoperated ignition means, said ''''memory'''' unit being deactivated eachtime said pneumatically operated valve means disconnects said fuelsource from said burner means whereby said ''''memory'''' unitterminates its output pneumatic signal until reactivated by said meansinterconnecting said pneumatic source to said pneumatically operatedignition means, said output pneumatic signal being required before saidmeans for interconnecting said pneumatic source to said pneumaticallyoperate valve means can interconnect said pneumatic source to saidpneumatically operated valve means, said ''''memory'''' unit providingan atmospheric output signal when in a deactivated condition thereof,said means interconnecting said pneumatic source to said pneumaticallyoperated ignition means interconnecting said pneumatic source to said''''memory'''' unit to not only cause sWitching of said ''''memory''''unit from its deactivated condition to its activated condition but alsoto terminate said atmospheric output signal during said switchingoperation and thereby prevent an atmospheric output signal during thetime said ''''memory'''' unit is being switched from its deactivatedcondition to its activated condition.
 2. A pneumatic control system asset forth in claim 1 wherein said pneumatically operated logic''''memory'''' unit comprises a housing means carrying a plurality ofspaced diaphragm means that move in unison relative to said housingmeans and cooperate therewith to define a plurality of chambers instacked relation.
 3. A pneumatic control system as set forth in claim 2wherein said pneumatic source is directed to one of said chambers toactivate said ''''memory'''' unit when said pneumatic source isinterconnected to said pneumatically operated ignition means wherebyanother chamber directs said output pneumatic signal from said pneumaticsource, and means interconnecting said other chamber with said onechamber to provide a holding pneumatic circuit means for said''''memory'''' unit in its activated condition.
 4. A pneumatic controlsystem as set forth in claim 3 wherein a restriction means interconnectssaid pneumatic source to said one chamber when said pneumatic source isinterconnected to said pneumatically operated ignition means.
 5. Apneumatic control system as set forth in claim 3 wherein said otherchamber and a third chamber of said ''''memory'''' unit have valve seatsleading thereto to be alternately opened and closed by said diaphragmmeans.
 6. A pneumatic control system as set forth in claim 5 whereinsaid valve seat of said third chamber is adapted to interconnect theatmosphere to its respective chamber when said diaphragm means openssaid valve seat of said third chamber and said source is disconnectedfrom said pneumatically operated ignition means.
 7. A pneumatic controlsystem as set forth in claim 6 wherein said valve seat of said otherchamber is adapted to interconnect said pneumatic source to itsrespective chamber when said diaphragm means opens said other valveseat.
 8. A pneumatic control system as set forth in claim 7 wherein saiddiaphragm means has passage means therein interconnecting said thirdchamber and said other chamber together.